This invention relates generally to analog-to-digital converters and, more particularly to an A/D converter using an acoustic charge transport delay line.
In the design of signal processing systems for high speed, high effective bit rate applications, total system performance can be enhanced by using GaAs devices at those points in the information path where very high processing rates are required, such as: signal acquisition, signal multiplexing/demultiplexing, specialty computation, analog-to-digital and digital-to-analog conversion. GaAs is generally being considered for interfacing and early signal processing because GaAs devices achieve very high processing rates with moderate levels of integration.
The Acoustic Charge Transport (ACT) device was developed by M. J. Hoskins and W. J. Hunsinger based on their observation of buried channel transport of majority carrier electrons by surface acoustic waves generated directly in GaAs. The basic ACT device is described in M. J. Hoskins et al., "Charge Transport by Surface Acoustic Waves in GaAs", Appl. Phys. Lett., 41(4), Aug. 15, 1982.
Typically, high speed A/D conversion is done using flash converters, which operate at very high rates, but which require a comparator and a reference voltage for each voltage step. N-bit resolution requires 2.sup.N comparators. Uniformity of threshold voltages for GaAs circuits is presently difficult to achieve, thus limiting the precision and yield for flash converters.
Therefore, it is an object of the present invention to provide a high speed A/D converter using GaAs circuitry.
It is another object of the present invention to provide a GaAs A/D converter using fewer comparators than present A/D converters.
Additional objects, advantages, and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention.